Isolation and developmental expression of the amphibian homolog of the fibroblast growth factor receptor 3.

Recent observations suggest that fibroblast growth factors (FGFs) and their receptors are involved in the control of embryogenesis. Several FGF receptor genes have been identified so far and their expression is differentially regulated. As part of a continuing effort to analyse the differential expression of FGF receptors and their potential role during amphibian development, we have isolated a Pleurodeles homolog of FGF receptor 3 (FGFR-3), which we designated PFR-3 because of its highest homology to human FGFR-3 (75% overall identity). PFR-3 is a maternally derived mRNA. While a low level of expression persists during the cleavage and gastrula stages, a significant increase in the mRNA was observed at the end of the gastrula stage. RNase protection analysis on dissected tissues showed that PFR-3 mRNA was mainly localized to the ectoderm at the early gastrula stage and then shifted to the embryonic neural tissues, whereas adult brain had decreased levels of PFR-3 mRNA expression. Consistent with the loss of FGF receptors during skeletal muscle terminal differentiation, PFR-3 as well as other FGF receptor mRNAs were undetectable in the adult skeletal muscle. However, highest levels of PFR-3 mRNA expression were found in the testis. In situ hybridization revealed strong expression in the germinal epithelium of the embryonic brain (especially the diencephalon and rhombencephalon) and neural tube, in the lens and the cranial ganglia. The epithelium of the developing gut, like the pharynx and esophagus, also prominently expressed PFR-3 mRNA. Other sites of expression were found in the liver and in the mesenchymal condensation sites of branchial arches.(ABSTRACT TRUNCATED AT 250 WORDS)